Merge ConstantInstr -> UnboxDouble to UnboxedConstant. Reduces register usage and allows for variou…

runtime/vm/flow_graph_optimizer.cc

Index: runtime/vm/flow_graph_optimizer.cc
===================================================================
--- runtime/vm/flow_graph_optimizer.cc	(revision 35632)
+++ runtime/vm/flow_graph_optimizer.cc	(working copy)
@@ -7594,6 +7594,9 @@
                                           Integer::Cast(left),
                                           Integer::Cast(right));
       SetValue(instr, Bool::Get(result));
+    } else if (left.IsDouble() && right.IsDouble()) {
+      // TODO(srdjan): Implement.
+      SetValue(instr, non_constant_);
     } else {
       SetValue(instr, non_constant_);
     }
@@ -8062,6 +8065,11 @@
 }
 
 
+void ConstantPropagator::VisitUnboxedConstant(UnboxedConstantInstr* instr) {
+  SetValue(instr, instr->value());
+}
+
+
 void ConstantPropagator::VisitConstraint(ConstraintInstr* instr) {
   // Should not be used outside of range analysis.
   UNREACHABLE();